Method of constructing tunnels



. Feb. 8, 1938. I M. l. KILLMER METHOD OF CONSTRUCTINC' TUNNELS FiledJuly 51, 1937 2 Sheets-Sheet l INVENTOR M795 [KY/27262" BY @5 4); 93ATTORNEYS .6 5 flaw,

Feb-8, 1938 M. I. KILLMER METHOD OF CONSTRUCTING TUNNELS 4 Filed July51, 1957 2 Sheets-Sheet 2 Patented Feb. 8, 1938 UNITED STATES PATENTOFFICE METHOD OF CONSTRUCTING TUNNELS Application July 31, 1937, SerialNo. 156,648

Claims.

This invention relates to an improved method of tunneling beneath riversand other bodies of Water.

When constructing a tunnel by the shield 5 method it is customary toadvance a shield through the ground and to build up the lining of thetunnel at the rear of the shield. The lining is usually composed ofmetallic segments having perforated flanges along their side edges bymeans of which the segments are bolted or riveted together but may becomposed of concrete or other material. When the tunnel is beingconstructed under a body of water this work has to be done undersufficient air pressure to prevent water from entering the shield.

When tunneling through yielding material such as silt, clay, and thelike, the greater portion of the material in the path of the shield isdisplaced upwardly, downwardly and sidewise and only a sufficient amountof the material is admitted into the shield to guide the shield in thedesired direction. Hence only a part of the material in the path of theshield has to be mucked out that is, removed by excavating with pick andshovel and tram car. On account of the comparatively impermeable natureof displaceable materials such as silt, clay and the like, there islittle tendency for the air under pressure within the shield to escapethrough the open end of the shield or between the tail of the shield andthe tunnel lining. Consequently, the tunneling operations can be carriedon with a moderate air pressure, with small constant loss of air andwith no danger of a blow, which is a sudden escaping of a large volumeof air at the face and consequently a sudden drop of air pressure in thetunnel.

On the other hand when the ground through which the shield is beingadvanced comprises unyielding porous material such, for example, assand, gravel, or the like or mixtures of such mateterials, Very little,if any, of the material in the path of the tunnel can be displaced bythe forward movement of the shield. Practically all the material in thepath of the tunnel has to be excavated within the shield and removedthrough the shield and the portion of the tunnel back of the shield.This greatly increases the time required to construct a tunnel of givenlength and correspondingly increases the cost. In addition, on accountof the porous nature of the material the air under pressure may escapein large quantities from the tunnel and pass upwardly through the sand,gravel or the like, and be lost.

Furthermore, because of the ease with which water can descend from theriver through the porous river bed and enter the tunnel, and for otherreasons, it is necessary to maintain a substantially higher air pressurewithin the tunnel in order to balance the water pressure and prevent itfrom entering the tunnel. Thus a greater amount of excavating work hasto be carried on under a much higher air pressure than when tunnelingthrough displaceable material such as silt or clay. The higher the airpressure the greater the danger to the laborers and others Working inthe shield and tunnel. Also the fact that this great amount ofexcavating work must be done under higher air pressure greatly increasesthe cost of construction on acount of the fact that the workmen are paidat a rate which increases very abruptly with the increase in airpressure, or, what amounts to the same thing, the number of hours perday which they are permitted by law to work are much shortened as theair pressure under which they are required to work is increased.

A further fact which increases the cost of tunneling through suchmaterial is that it is often necessary to lay a clay blanket on the bedof the river in order to weigh down the porous unyielding materialthrough which the tunnel is to be built. This clay blanket helps toreduce the loss of air through the porous material and provides theweight necessary to prevent the higher air pressure required by theporous material from escaping suddenly and disastrously in a blow.

The object of my present invention is to provide an improved method oftunneling through unyielding porous material under conditions where highair pressures are usually required in order to prevent water fromentering the tunnel, which will enable such tunneling operations to becarried on under greatly reduced air pressure, thus enabling the work tobe done with greater safety and at less expense.

The invention also aims to reduce or eliminate entirely the necessity oflaying the clay blanket above referred to on the river bed and togreatly reduce the amount of material which has to be excavated throughthe tunnel shield.

In accordance with my present invention, when a tunnel is to beconstructed through unyielding porous material beneath a body of water,I propose to excavate a trench in such material forming the bed of thebody of water, this excavating work being done from the surface of thewater, preferably by means of an appropriately constructed dredgingapparatus. Where conditions permit, this trench is to be excavated to adepth a material which is easily tunnelable, such, for

example, as clay, silt, or the like. After the refilling of the trenchin this manner, I propose to drive the tunnel, or tunnels, through thiseasily tunnelable material employing a shield, or shields, and advancingthem through the displaceable material in the customary manner whentunneling through such material.

In the accompanying drawings, the method of my invention has beenillustrated diagrammatically. In these drawings:

Fig. 1 is a vertical section taken transversely of the path, orright-of-way, of the tunnel before tunneling operations are commenced;

Figs. 2 and 3 show similar views after two of the steps have beencarried out;

Fig. 4 is a similar viewafter the tunnels (in this case two) have beencompleted;

Fig. 5 is a view similar to Fig. 3 showing the completion of one of theintermediate steps of building a tunnel through a somewhat differentearth formation than that shown in Figs. 1 to 4, inclusive;

Fig. 6 is a view similar to Fig. 5 after the completion of a furtherintermediate step; and

Fig. 7 is a similar view after the tunnels have been finished.

- Referring now to these drawings, in Fig. 1 the body of water, river,bay, etc. is indicated by reference numeral I and the bed of the riverby reference numeral 2. Thematerial indicated by reference numeral 3comprises a deep layer of sand and gravel which, in Figs. 1 to 4,inclusive, extends to a depth greater than the bottom of the tunnel andrests upon rock which is indicatcdby numeral 4. r

In Fig. 2 a trench 5 has been excavated to a depth below that at whichthe bottoms of the tunnels are to be located. This trenchextends in thedirection of the tunnels and in the event that the upper surface of therock 4 does. not rise. above the level of the bottom of the tunnels atany point, this trench will be excavated to a uniform depth, such asindicated at Fig. 2, throughout the entire width of the river, or otherbody of water. I

T As shown in Fig. 3, the trench 5 has been filled with a yielding, ordisplaceable, material 6, such I for example, as clay, and in Fig.ethetwo tunnels 1 and 8 have been driven through the clay 6 within thetrench. In laying the clay 6 within trench 5 it is preferable, ifconditions will permit; not to fill the trench entirely full, but toleavedepressions, or hollows, 9 above the locations of the tunnels I and8, since the driving of the tunnels through the clay forces the materialupwardly and levels it off, as shown in Fig. 4. It will be understoodthat this cannot be done unless the tunnels are to be located asubstantial distance below the bottom of the river bed; there must be asufficient depth of clay above the tops of the tunnels to prevent theair pressure within the tunnel from blowing up through the .end of thetunnel shield.

" The earth formations through which it may be desirable to tunnel varya great deal, and in Figs. 5 to 7 inclusive, a formation is shown inwhich the layer of sand and gravel 39, between the surface of the rock4a and the bed of the river 2a, is shallower than that indicated in thepreceding figures. In order to place the tunnels 1a and 89, at thedesired depth, the bottoms of the tunnels must be below the uppersurface of the rock formation 45. Under such circumstances, it is morepractical to excavate the shallower trench 59, than to dig the trenchclear down to the surface of the rock 4a. The trench 5a isthereforeexcavated to a depth below the top of the tunnels 1a and 8a andthe trench is filled with silt, or clay, 6a. The trench 5a is excavatedto a depth below the 'top of the tunnels sufiiciently to permit thedumping of the impermeable material at such a depth that, for example,the upper third of the face will be in impermeable and "yieldingmaterial and hence the upper third of the shield may be kept closed witha consequent reduction in the constant-loss of air through the face anda consequentreduction or entire elimination of the danger of a blow orsudden loss of all of the air in the tunnel.

Bulkheadsmay'be built in the tunnel shields extending downwardly fromthe tops of the' shields to approximately the level of the bottom of thetrench 53,, that is to say, the line of demarcation between sand andgravel and clay.

The clay, being displaceable by the movement of the tunnel shield, doesnot have to be excavated, or mucked out, through the tunnel shield, butis pushed aside by the bulkheads.

While the full advantages of my invention cannot be availed of whentunneling through such formations, since the sand and gravel and rock inthe paths of the tunnels must be removed through the shield by pick andshovel, the rock being first blasted to loosen the same, nevertheless itis extremely desirable to employ the improved method. In the first placethe placing of the dense, yieldable clay 63, above the tunnels andsurrounding the upper portions thereof greatly reduces the directpassage of water from the river vertically downward into the tunnelshields and reduces the escape'of air and the consequent danger ofblowing through to the surface of the river. This makes the tunnelingoperations much safer for the workmen, and, in addition, greatly reducesthe cost of construction.

A further advantage is the fact that the amount of material which has tobe removed through the tunnel shields is'reduced proportionally to thedistance below the tops of the tunnels through which the trench 5a isexcavated, this material being displaced to one side by the bulkheads ofthe tunnel shields.

When the tops of the tunnels 7 and 8 must necessarilybe located at acomparatively shallow distance'below the bottom of the river, it may benecessary to fill in the trench 5s withthe dense yielding clay materialto a depth somewhat greater than the normal levelof the river bed 25,,as indicated in Fig. 6. In other words, in addition to filling thetrench'5 a 'clay blanket llJ may advantageously be laid over the tunnels andthen dredged out after the tunneling operations are completed. Underthese circumstances, the laying of the objectionable clay blanketreferred to heretofore is .not entirely eliminated, but the blanket isreduced in thickness to a comparatively small fraction of the depth ofclay blanket which would be necessary if the method of my inventionshould not be employed and the tunnel should be constructed through thesand and gravel and rock without excavating the trench 5a and filling itwith the dense, yieldable material 6*.

Reviewing briefly the advantages of the present invention, although agreater amount of material must be excavated to dig the trenches 5 or 5athan would be necessary to excavate under the present practice, theexcavating work can be done by machine rather than by hand. This machinewhich consists of a deep dredging apparatus operating from the surfaceof the river, can be operated by workmen who are working comfortablyunder normal atmospheric pressure conditions rather than under airpressure within the tunnel shield. This excavating work can be donewithout any unusual hazards, and consequently no wage premium has to bepaid.

- When the tunnels themselves are being driven, the air pressure underwhich the men work will be in most cases, greatly reduced, therebyresulting in greater safety and reducing the wage premium to a minimum.

It will be understood that the conditions of earth formation throughwhich it may be desired to construct tunnels vary a great deal and thatunder some conditions full advantage of the invention can be taken,whereas under others, only some of the advantages may be made use of. Itmay occur also that full advantage of the invention may be taken foronly a part of the construction of a given tunnel. Due to changes in theearth formation along the proposed tunnel route, it may be possible toexcavate the trench 5 to full depth, as shown in Figs. 1 to 4,inclusive, for only a portion of the distance, whereas along otherportions of the route it may be necessary to excavate the trench to lessthan full depth, as shown in Figs. 5 to 7, inclusive. In either event,however, wherever it is possible to take advantage of the principle ofmy invention, the tunnel operations may be carried on with greatersafety, more expeditiously, and at less cost than if the tunnel wereconstructed following the methods employed heretofore.

I claim:

1. The method of tunneling through porous material beneath a body ofwater which comprises excavating a trench in the porous material,filling the trench with yielding and impermeable material, and advancingthe tunnel through said yielding material.

2. The method of tunneling through porous material beneath a body ofwater which comprises excavating a trench in the porous material to somelevel below the top of the tunnel but above the bottom thereof, fillingthe trench with yielding and impermeable material and advancing 60 thetunnel through material comprising said yielding and impermeablematerial in the upper part of the tunnel and the original porousmaterial below.

3. The method of tunneling through porous material beneath a body ofwater which comprises excavating a trench in the porous material,

filling the trench with yieldable material having greater density thanthe excavated material and advancing the tunnel through said yieldablematerial.

4. The method of tunneling through porous material beneath a body ofwater which comprises excavating a trench in the porous material to adepth below the top of the tunnel, filling the trench with easilytunnelable material, and advancing the tunnel partly through the porousmaterial and partly through the easily tunnelable material.

5. The method of tunneling through porous material beneath a body ofwater which comprises excavating a trench in the porous material to adepth below the bottom of the tunnel, filling the trench with easilytunnelable material, and driving the tunnel through said easilytunnelable material.

6. The method of tunneling through porous material beneath a body ofwater which comprises excavating a trench in the porous material to adepth below the top of the tunnel and above the bottom thereof, sealingthe upper portion of the tunnel shield from the top to the level of thebottom of the trench, filling the trench with easily tunnelablematerial, and advancing the tunnel partly through the porous materialand partly through the easily tunnelable material, the latter materialbeing displaced by the advance of the tunnel shield.

'7. The method of tunneling through porous material beneath water whichcomprises excavating a trench in the porous material to a level belowthe top of the tunnel but above the bottom thereof, filling the trenchwith easily tunnelable material to a level substantially above the topof the tunnel, and advancing the tunnel through material comprising saideasily tunnelable material in the upper part of the tunnel and saidporous material below.

8. The method of tunneling through porous material beneath water whichcomprises excavating a trench in the porous material to a level belowthe top of the tunnel but above the bottom thereof, filling the trenchwith clay, silt or the like to a level substantially above the top ofthe tunnel, and advancing the tunnel through material comprising saidclay, silt or the like in the upper part of the tunnel and said porousmaterial below.

9. The method of tunneling through porous material beneath water whichcomprises excavating a trench in the porous material, filling the trenchwith easily tunnelable material to a level substantially above the topof the finished tunnel, and advancing the tunnel through said easilytunnelable material.

10. The method of tunneling through porous material beneath water whichcomprises excavating a trench in the porous material, filling the trenchwith clay, silt or the like to a level sub.- stantially above that ofthe finished tunnel, and advancing the tunnel through said clay, silt orthe like.

MILES I. KILLMER.

